Thin polished plates such as silicon wafers and the like are a very important part of modern technology. A wafer, for instance, may refer to a thin slice of semiconductor material used in the fabrication of integrated circuits and other devices. Other examples of thin polished plates may include magnetic disc substrates, gauge blocks and the like. While the technique described here refers mainly to wafers, it is to be understood that the technique also is applicable to other types of polished plates as well. The term wafer and the term thin polished plate may be used interchangeably in the present disclosure.
Wafers are available in a variety of sizes. They may also be patterned or presented as bare wafers. Interferometer wafer metrology systems, such as WaferSight metrology system from KLA-Tencor, may scan both the front and back surfaces of a wafer at the same time. By combining wafer shape, edge roll-off, thickness or flatness, and topography measurements in a single scan, such wafer metrology tools may provide complete data sets that are necessary for topography and wafer geometry monitoring in wafer manufacturing.
It is noted, however, that the resolutions of the imaging devices utilized in some of the interferometer wafer metrology systems may not be able to fully resolve certain patterned wafer surfaces, limiting the accuracies of such metrology systems in patterned wafer geometry. Therein lies a need for systems and methods for enhancing wafer geometry measurements, particularly for patterned wafers, and utilizing the enhanced measurements for various monitoring and design purposes.